The present invention is directed to new and distinct strains of the higher Basidiomycetes edible mushrooms which are adapted to grow in biomass form in submerged culture containing especially formulated nutrients.
Edible higher Basidiomycetes mushrooms have been used in folk medicine since ancient times. They include species from the Basidiomycetes class that have macroscopic fruit bodies, also known as basidioma or basidiocarp. These fruit bodies can be either hypogeous or epigeous, large enough to be seen with the naked eye, and can be picked by hand. Higher Basidiomycetes contain approximately 10,000 species from 550 genera and 80 families. The distinguishing characteristic of Basidiomycetes is the presence of basidium leaving exogenous basidiospores as a result of meiothic process.
The typical life cycle involves the germination of the basidiospore to give a primary haploid mycelium, which in turn becomes a secondary mycelium. Nuclear fusion takes place in the young basidium and meiosis takes place before basidiospore development. The macroscopic basidioma is generally fleshy and takes a variety of forms including terrestrial or hypogeneous, lignicolous or saprobic, mycorrhizal or pathogenic, edible, medicinal, hallucinogenic or poisonous mushrooms. Hawksworth D.L. et al, 1995, in Ainsworth and Bisbi""s Dictionary of the Fungi, 8th ed. CAB International, University Press, Cambridge p. 616.
The most popular species of cultivated edible mushrooms include Agaricus bisporus (J Lge) Imbach, A. bitorquis (Quxc3xa9l.) Sacc, Lentinus edodes (Berk) Sing., Pleurotus spp., Auricularia spp., Volvariella volvacea (Fr) Sing., Flammulina velutipes (Fr.) Sing., Tremella fuciformis Berk., Hypsizygus marmoreus (Peck) Bigel., Pholita nameko (T. Ito) S. Ito et Imai, Grifola frondosa (Dicks.: Fr.) S.F. Gray, Hericium erinaceus (Bull: Fr.) Pers., Dictyophora indusiata (Vent.: Pers.) Fischer, Stropharia rugosoannulata Farl. apud Murr., Lepista nuda (Bull.: Fr.) Cooke, Agrocybe aegerita (Brig.) Sing., Pleurotus citrinopileatus Sing. In 1994, the world production of cultivated edible mushrooms was estimated to be approximately five million tons, which was valued at about ten billion dollars (US).
The cultivation of fruiting bodies of mushrooms deals with living organisms, for example, the mushroom itself and other microorganisms which may either be harmful or beneficial. Therefore, the methods employed in mushroom cultivation require modifications depending upon the region being cultivated, substrates available, environmental conditions and species of microorganisms encountered. The cultivation of mushrooms for fruit bodies production is a long-term process needing from one to several months for the first fruiting bodies to appear. In the present invention, the growth of pure mushroom cultures in submerged conditions on a liquid culture media permits to accelerate their growth, resulting in large biomass yields within a few days. Optimization of the culture medium composition and physicochemical conditions of growth allows regulation of fungal metabolism, and in turn obtain high yields of the biomass. It also allows production of large amounts of specific mushrooms which are rich in specific medicinal components and/or others nutritional substances of constant composition. The data are obtained on the quantitative chemical composition and identity of submerged mycelial biomass and carpophores in varieties of higher Basidiomycetes mushrooms.
The present invention is directed towards higher Basidiomycetes mushrooms of the genus Pleurotus grown in submerged culture on nutrient media. The outstanding characteristics of these higher Basidiomycetes mushrooms growing as a biomass in submerged cultures are their shorter incubation period within a few days in the nutrient media comparing with standard fruiting Basidiomycetes mushroom varieties, and the increased yields of biologically active compounds such as protein rich in the essential amino acids and vitamins serving as functional foods compared with the yield of these components in carpophores of the standard fruiting Basidiomycetes mushrooms.